The present invention concerns a mouthwash solution intended to prevent enrichment of heavy metals in the oral cavity on mucous membranes and dental surfaces.
In corrective dental care metallic materials are used in rather great profusion, such as tooth fillings and crown materials; the number of different materials is estimated to be more than one hundred. Usually these materials are composed of four or five different metals and compounds thereof.
For metallic filling material is used amalgam filling, which is typically prepared of mercury (contribution about 45-55%) and of a premix, which typically has had the composition: Ag 67-70%, Sn 25-29%, Cu 0-5%, Zn 0-2%. In modern amalgam fillings, however, copper tends, owing to price considerations, to replace silver, its quantity rising even up to 30%.
Actual prostheses, i.e., crowns, are made outside the oral cavity by casting a metal duplicate corresponding in its structure to the extracted tooth, or a metal blank which is overlaid with ceramic enamel to simulate the structure of the tooth. High-gold materials have traditionally been the best material to serve this purpose. In order to replace gold and to optimize the properties of the alloy (mechanical characteristics, castability, corrosion resistance, metal/ceramic bond, thermal expansion) other metals, also less noble ones, have to be added (Pt, Pd, Ag, Cu, Fe, Sn, Zn, In, Ga, etc.). The composition of the materials which are used and the contribution of base metals vary considerably both from manufacturer to maunfacturer and in accordance with the requirements imposed on the prosthesis.
The problem in dental care of the kind just described have been allergic reactions of patients, especially in risk groups like asthmatics, who on the whole are disposed to allergic reactions. The cause responsible for these reactions is the dissolving of heavy metals in the mouth from dental care materials. These heavy metal effusions tend to become enriched and to accumulate in the oral cavity on dental surfaces, darkening them, and particularly on mucuous membranes.
We have found that those patients in whom allergic symptoms have been observed have in their saliva and in their oral cavity metal residues in quantities which should be reduced. In our studies we have established the cause of certain diseases of the oral mucous membranes to be allergic irritation from metals. It is also likely that contact allergy in the oral cavity may acerbate the cell picture of incipient cancer of the mouth.
We have observed in our studies that all metals here in question cause allergies of the oral cavity. One patient may moreover simultaneously have allergies from several metals.
Nobler metals and noble metal-based homogeneous metal alloys are not in themselves likely to react with saliva, which a weak electrolyte and one of which the acidity is close to neutral.
The situation is substantially changed, in principle, when there are concomitantly several metallic materials in the mouth which differ as to their electrochemical nature.
The difference between metals in electrochemical respect is commonly described with the aid of the so-called electrochemical potential series, which gives a simple picture of the differential potentials acting between different metals. Thus, for instance, when gold and copper are in mutual contact said differential potential tends to dissolve copper, which in itself would be comparatively stable in the circumstances.
The amount in which heavy metals are dissolved in saliva is dependent on a number of factors, e.g. on how direct is the contact between the metals, and on the homogenity of the alloy. Even from an alloy rich in noble metals there may be even rapid dissolving in saliva of components which are only little less noble. Of course, conditions for dissolution of heavy metals are particularly favourable in connection with tooth filling, burnishing and bridge and crown grinding and thereafter.